Method of forming light guides

ABSTRACT

THE MANUFACTURE OF LIGHT GUIDES WHEREIN A CONTINUOUS FILAMENT IS WOUND ONTO A FORMER WHILST THERE IS RELATIVE MOVEMENT AXIALLY OF THE FORMER OF A FILAMENT GUIDE MEANS TO FORM AN ENDLESS BUNDLE OF FILAMENT LOOPS WHICH IS SEVERED APPROPRIATELY TO PRODUCE THE REQUIRED LIGHT GUIDE.

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, METHOD OF FORMING LI GHT GUIDES SUBSTHUTE FOR wnssme XR Filed Feb. 24. 1969 BOON"! United States Patent 0 US. Cl. 29-412 10 Claims ABSTRACT OF THE DISCLOSURE The manufacture of light guides wherein a continuous filament is wound onto a former whilst there is relative movement axially of the former of a filament guide means to form an endless bundle of filament loops which is severed appropriately to produce the required light guide.

This invention relates to a method of forming light guides each consisting, as is well known, of a compact bundle of filaments of light transmitting material, and relates to light guides formed according to the method. The invention is particularly adapted to the production of Y guides, but can also be used for the production of multitail guides and indeed single guides which, in length, may

be made in greater dimensions than is at present possible under normal manufacturing conditions.

Broadly, the invention provides a method of forming a light guide made up of a compact bundle of light transmitting filaments, comprising winding a continuous filament of light transmitting material into a former, effecting relative movement between the former and a guide means which holds the filament as it is wound onto the former, said relative movement being in a direction transverse to the direction of movement of the filament through the guide means, so that the filament is laid repeatedly over the same endless loop on the former to form an endless bundle of filament loops, with at least one crossing point, and severing the bundle to form the light guide.

Conveniently, the relation between the speeds of the rotary and traverse movements are so adjusted as to result in a figure of eight winding or a succesion of such figures extending circumferentially around the surface of the former.

Instead of a figure of eight formation, the filament can be wound as an open reentrant helix.

For the formation of a Y guide, the winding is first carried out as a figure of eight Winding and the resultant bundle is thereafter severed at'the cross over position.

In order that the invention may be more clearly understood some preferred examples will now be described with the aid of the accompanying drawings in which:

FIG. 1 diagrammatically illustrates a Y type of guide as made under existing conditions;

FIG. 2 is a similar view of the same type of guide made in accordance with the present invention;

FIGS. 3 to 6 illustrate respectively individual examples of the formation of guides all lying within the present invention.

As shown in FIG. 1 two separate bundles of filaments 10 and 11 are joined together into Y formation to be present and to terminate in a common end face 12; but owing to the separate formation of the bundles the filaments from the two bundles are not uniformly distributed over the end face but are, to all intents and purposes, divided into two groups each covering approximately half the total area of that face. This is indicated by shaded and unshaded portions shown in, the end face. By winding the filament in accordance with the present invention 3,585,705 Patented June 22,, 1971 the two bundles are more or less uniformly distributed and intermingled over substantially the entire end face as indicated in FIG. 2.

In order to make a Y guide having the distribution according to FlG. 2, a single filament is Wound on to a cylindrical former 13, FIG. 3, which latter is rotated about its axis 14 and at the same time a guide through which the filament is fed to the former is continuously traversed back and forth axially of the former, the relation between the speeds of rotation and traverse being so chosen and adjusted that a figure of eight winding results. Subsequently, the bundle can be severed along the line XX thereby providing a junction terminating in an end face with a filament distribution similar to that shown in FIG. 2. In order to make two Y guides the bundle will also be severed at Z-Z in two places.

Alternatively, the winding could be carried out to provide the formation shown in FIG. 4 which, when the bundles are severed at X-X and also in similar positions to those marked Z--Z in FIG. 3 several Y guides can be formed all at the same time.

It is to be understood that the invention also lends itself to the formation of multi-tailed guides. For instance if the cut is made at XX in FIG. 4 and the ends on one side only of the cut are freed, a guide with five tails would result. This arrangement of winding can be modified to suit the number of tails required.

A still further method is indicated in FIG. 5 where the relative rotational and traverse speeds are adjusted to form a succession of cross over positions peripherally spaced around the surface of the former.

Should it be desired to produce an extended guide as a single length, instead of severing the figure of eight winding produced as in FIG. 3 at X-X and Z-Z the bundle can be severed at A-A and the short end extending beyond the cross over carefully pulled out thus leaving a single length light guide.

Another method of forming a single relatively long guide is indicated in FIG. 6 in which the filament is wound as an open reentrant helix which can be severed at AA and the end thus provided carefully pulledout from the successive coils of the helix.

All the forms of winding described above result in open figures of convolution which have hereinbefore been referred to as skeletonised open reentrant figures, and this expression is to be understood as including any such figure as may be desired in order to produce light guides by a method of combined winding and traverse motions.

After severing the bundle at XX as in FIGS. 3, 4 and 5, the junction can be reinforced by binding or any other preferred means in order to assure that one bundle of filaments shall not be easily pulled out from the other bundle. This may be necessary owing to the relatively short junction provided at the crossover position. Alternatively, provision can be made, prior to the commencement of winding, for positioning a binding strip to be subsequently tightened before actually severing the bundle.

Alternatively, at the position of cross over as in FIG. 3, the circumferential length of the cross over portion can be extended so that after severence a sufiicient length of the stem part of the Y remains and will be self supporting without the need for reinforcement.

What is claimed is:

1. A method of forming a light guide made up of a compact bundle of light transmitting filaments, comprising the steps of:

(a) winding a continuous filament of light transmitting material into a former;

(b) effecting relative movement between the former and a guide means which holds the filament as it is would onto the former, said relative movement being 3 in a direction transverse to the direction of movement of the filament through the guide means, so that the filament is laid repeatedly over the same endless loop on the former to form an endless bundle of filament loops, with at least one crossing point; and

(c) severing the bundle to form the light guide.

2. The method according to claim 1, including the step of arranging for the relative movement and the speed of Winding of the filament to be such that the bundle of filament loops is of figure eight formation.

3. The method according to claim 2, including the step of severing the bundle at the crossing point and at each of the loops of the figure eight formation so as to form two Y-guides.

4. The method according to claim 2, including the steps of severing thebundle of filament loops in one loop of the figure eight formation at a location close to the crossing point and carefully drawing the short length of the bundle of filaments between the crossing point and the location of the sever through the crossing point so as to produce a single light guide.

5. The method according to claim 1, including the step of arranging for the relative movement and the speed of winding of the filament to be such that the bundle of filament loops extends round the former in wavey or sinuous path and there are several crossing points.

6. The method according to claim 5, including the step I of severing the bundle of filament loops at each crossing point and at appropriate other points to make twice the number of Y-guides as there are crossing points.

7. The method according to claim 1 including the step of arranging for the relative movement and the speed of winding of the filament to be such that there is a crossing 1 point where a multiplicity of reaches of the endless bun dle of filament loops meet.

8. The method according to claim 7 including, the step of severing the bundle of filament loops at said crossing point to form a multi-tail light guide.

9. A method according to claim 1, including the steps of arranging for the speed of rotation and the rate of winding the filament to be such that the endless bundle of filament loops takes up the form of a helix on the former with an axially extending reach joining the ends of the helix and forming crossing points with the coils, severing the bundle at a point on said reach which is displaced from the crossing points, and drawing one severed end carefully through crossing points to form a single light guide.

10, A method according to any preceding claim including the steps of rotating the former and moving the guide means transverse to the direction in which the filament moves through the guide means, to provide the combined winding and laying movements.

References Cited UNITED STATES PATENTS 2,664,375 12/1953 Slayter 65-4 2,843,153 7/1958 Young.

3,448,180 6/1969 Opferkuch et al 2641 3,467,507 9/ 1969 Andreevskaya et :11.

JOHN F. CAMPBELL, Primary Examiner D. C. REILEY, Assistant Examiner U.S. Cl. X.R. 294l9, 423; 65-4; 264-1 

